A conventional way of dispensing volumes of liquids is to fill a translucent pipe up to a certain fill level. Upon reaching the desired fill level, the liquid surface is detected by means of a light barrier. Here, one takes advantage of the fact that the refractive index of the liquid to be dispensed is very different from the refractive index of air. Therefore, a filled pipe will refract the light of the light barrier differently than an unfilled pipe. A light receiver registers this difference. If the pipe is filled up to the light barrier, the filling is stopped, and the contents of the pipe can be emptied as measured volume and used further. If several different volumes are to be dispensed, then several light barriers will need to be used. A disadvantage here is that the ratio of the smallest possible to the largest possible dispensing volume is dependent upon the spatial requirements of a light barrier and the length of the pipe.
DE 10 2013 114 138 A1 contains an analytical device for determining a parameter of a liquid sample, comprising a container system for storing samples, reagents, and waste products in containers and a conveyor and dispensing system for metering and conveying the sample and reagents from the containers into a metering vessel and for disposal of waste products from the metering vessel into a waste container. The conveyor and dispensing system are designed as a metering vessel for removal of a predetermined volume of a liquid as a liquid sample from a sample-taking location.